Companion virus
Virus using the name of a common system file
A companion virus is one which, rather than injecting its code into another file, takes its place instead. Commonly targeted files for such viruses are ones that are in regular use, especially on system startup, which ensures the virus is executed.
Companion viruses operate by replacing files, either in the same location, deleting or renaming the original, or by placing themselves somewhere ahead of the original file in the path. Some companion viruses also run the original file once they are activated, to ensure the system runs properly and to cloak their own presence.
